In this Phase II SBIR Luna Innovations will perform human subject tests of the EN-TACT(tm) Patient Monitor to determine the sensitivity and specificity of diagnosis of compartment syndrome as compared to slit-catheter measurements of intramuscular pressure (IMP), the current gold standard measurement. A Phase I animal model showed that the EN-TACT(tm) Patient Monitor is substantially more sensitive than diagnosis by clinical signs (73% vs. 13-19%) with comparable specificity (93% vs. 97%), as reported by Ulmer (2002). The objective of this Phase II SBIR is to improve the diagnostic accuracy in human subject tests. To achieve this objective, three specific aims for the Phase II research are: (1) Reduce subject-to-subject variability in tissue displacement signal by eliminating operator dependant variations in probe placement and interpretation of which ultrasonic echo corresponds to which anatomical feature. (2) Establish diagnostic utility in human subjects using model compartment syndromes of the lower leg and abdomen. (3) Verify diagnostic utility in clinical tests at the UCSD School of Medicine, Eastern Virginia Medical School, the University of New Mexico School of Medicine and the College of William and Mary Sports Medicine Department. PUBLIC HEALTH RELEVANCE: There is a great need for improved diagnosis of compartment syndrome, as inaccuracy in the current methods of diagnosis often lead to delays in treatment. Missed diagnosis of compartment syndrome to be one of the most common causes of litigation against doctors in North America, with the average malpractice award from a missed compartment syndrome case approximately $280,000 in 1993. In the absence of good diagnostic tools for compartment syndrome, anecdotal evidence suggests that the fasciotomy - a surgical opening of the muscle fascia to release compartment pressures - is often performed prophylactically, subjecting the patient to a long and expensive recovery that might otherwise be avoided.